1. Field of the Invention
The present invention relates to a rotation velocity sensor for a reel disk used in a tape recorder, and more particularly, to an improved rotation velocity sensor for a reel disk which has fewer components and is easier to assemble.
2. Description of the Related Art
FIG. 1 illustrates a device for detecting the rotation velocity of a reel disk in a tape recorder. White light-reflecting portions 3 and black light-absorbing portions 4 are alternately and radially disposed on a reflector 2 which is attached to the bottom of a reel disk 1. A light sensor 5, emits light onto reflector 2 and detects rotation velocity variation based on the light reflected by reflector 2, so that the rotation velocity of reel disk 1, which is varied according to the winding amount of the tape, is detected.
However, the conventional rotation velocity sensor requires the reflector 2 in which light reflecting portion 3 and light absorbing portion 4 are radially and alternately arranged. This increases production cost. Further, since reflector 2 is attached to the bottom of the reel disk, assembly time is increased.